Behemoth is the male couterpart to LEVIATHAN, one of the fallen angels and a demon of the deep. Like Leviathan, Behemoth is associated with RAHAB and the sea, and is personified variously as a whale, crocodile and hippopotamus. He also is associated with the ANGEL OF DEATH. Behemoth is sometimes described as being overweight and stupid. It is the reason why he encourages gluttony and the pleasures that satisfy hunger. He shapeshifts to various animal forms, and often is depicted as an elephant with a huge stomach.
The Book of Enoch, an apocryphal work, says that Behemoth and Leviathan were separated by God at the time of creation. Leviathan was sent to the sea and Behemoth was sent to an immeasurable desert named Dendain. In the Bible, Job 40:15 - 24 describes Behemoth as a mighty beast, "the first of the works of God" (40:19). Rabbinic lore holds that on the Day of Judgement, he will slay and be slain by Leviathan. His fate is to produce meat for the Messiah's feast, and his flesh will be distributed to the faithful. Another rabbinic legend says that God destroyed Leviathan on the day he created both monsters, but placed Behemoth in the form of a giant ox, on enchanted mountains to fatten him up. There he eats the grass of one thousand mountains each day; the grass grows back each night. Behemoth is doomed to remain there alone until the end of time, because God realized that such a monster could not be loosed upon the world.
"In Christian lore, Behemoth is considered one of the prime representations of evil. The demonologist Johann Weyer, who catalogued the ranks of hell, did not include Behemoth in his list, but did include him in another work, Praestigiorum Daemonum, in which he suggested that Behemoth represents Satan himself. Other demonologists of medieval times did include Behemoth in their rankings."
~ The Book of Demons, Victoria Hyatt and Joseph W. Charles.